This invention relates to rotary compressors or blowers, particularly to blowers of the Roots-type. More specifically, the present invention relates to a method of assembling such blowers and to a fixture for timing the rotors and gears of such a blower.
Rotary blowers, particularly Roots-type blowers employed as superchargers for internal combustion engines are well-known in the prior art. However, they have not been widely used, particularly in passenger cars for several reasons since they, in general, have been characterized by several problems such as noisy operation, relatively high manufacturing and assembly costs, low efficiency and/or poor durability. Quite often, all or many of these problems are related to the basic design of a few components in such blowers since these basic designs often dictate machining costs and/or assembly methods which in turn may lead to one or more other problems such as noise, efficiency, and/or durability.
For example, during assembly of prior art rotary blowers, considerable time and effort are required to properly locate the rotors within the blower housing and to properly locate or time the meshed lobes of the rotors with respect to each other. Such meticulous locating and timing are necessary due to the fact that the rotors should have a very slight running clearance with the blower housing surfaces and likewise the meshed lobes of the rotors should have a very slight running clearance therebetween. Contact with the blower housing or between the meshed gears soon causes the blower to lose efficiency and/or fail. In the prior art, the rotors and their associated shafts and timing gears were either premachined to provide such locating and timing or were machined during assembly to provide such locating and timing. Both of these machining practices had to be extremely accurate, were naturally very expensive, were not conducive to fast and inexpensive assembly as required in a mass-production environment.
Herein is disclosed a rotary blower or supercharger designed to negate or substantially reduce all of the above-stated problems. For example, the rotors, shafts, and timing gears of the supercharger disclosed herein require no premachining or machining during assembly to effect proper timing. Further, the shafts may be pressed into the rotors without concern of phase relation or timing. Still further, the supercharger may be partially assembled and one of the timing gears installed without concern of phase relation or timing. Additionally, the supercharger disclosed herein is designed to be accurately and quickly timed during assembly by a specially designed fixture.